DayOfMonth

' this is the subroutine that used the function. 
' the prefix "udb" stands for up/down button which is a 
' standard microsoft control.

Private Sub udbDateChange_UpClick()
 ' this subroutine handles the user clicking on the up 
 ' arrow to change dteStartDate and dteEndDate are module 
 ' level variables.
   Dim intNumDays As Integer
 ' this will increment the start and end dates
   dteStartDate = DateAdd("m", 1, dteStartDate)
 ' this was defaulted at form load
   intNumDays = DaysInMonth(dteStartDate)
   dteEndDate = DateAdd("d", intNumDays - 1, dteStartDate)
   txtStartDate.Text = Format(dteStartDate, "mm/dd/yyyy")
   txtEndDate.Text = Format(dteEndDate, "mm/dd/yyyy")
End Sub
 Inputs:
a starting date either input from user or defaulted 
to current date.

Public Function DaysInMonth(ADate As Date) As Integer
' this function will determine number of days in a month

Dim dteNextMonth As Date
Dim dteCurMonth As Date
' set the day of the month passed in to the 1st day

dteCurMonth = CDate(DateAdd("d", -Day(ADate), ADate) + 1)
dteNextMonth = DateAdd("m", 1, dteCurMonth)
' determine the number of days

DaysInMonth = DateDiff("d", dteCurMonth, dteNextMonth)
End Function

' this is the subroutine that used the function.

' the prefix "udb" stands for up/down button which is a

' standard microsoft control.

Private Sub udbDateChange_UpClick()
' this subroutine handles the user clicking on the up

' arrow to change dteStartDate and dteEndDate are module

' level variables.

Dim intNumDays As Integer
' this will increment the start and end dates

dteStartDate = DateAdd("m", 1, dteStartDate)
' this was defaulted at form load

intNumDays = DaysInMonth(dteStartDate)
dteEndDate = DateAdd("d", intNumDays - 1, dteStartDate)
txtStartDate.Text = Format(dteStartDate, "mm/dd/yyyy")
txtEndDate.Text = Format(dteEndDate, "mm/dd/yyyy")
End Sub
Inputs:
a starting date either input from user or defaulted
to current date.